The invention relates generally to non-conductive hollow structures, and more particularly, to a system for estimating a condition of a non-conductive hollow structure exposed to a lightning strike.
Wind turbine blades have become increasingly susceptible to lightning strikes, as the rated electric power of the wind turbines and the dimensions of the wind turbine blades have increased. The condition of a wind turbine blade exposed to a lightning strike can be adversely affected. This can result in reduced power output, as it requires long down time to repair and/or replace the affected blade.
Conventional systems have been proposed to protect wind turbine blades from adverse condition effects due to lightning strikes. In such systems, wind turbine blades are equipped with a metal receptor at a tip of the blade and a down-conductor is installed within the interior of the blade, to electrically couple the metal receptor to an earth ground. Other designs of conventional down-conductor systems may include external meshes or external conductors, for example. In the event of a lightning strike to the metal receptor at the blade tip, the conductor passes a lightning current from the blade tip to the earth ground, in an effort to prevent the lightning current from causing adverse condition effects to the turbine blade.
However, such conventional systems may have several drawbacks. For example, not all lightning strikes to the wind turbine blade occur at the blade tip. Instead, the lightning may strike the wind turbine blade at an intermediate location between the root and the tip of the blade, with the potential to cause adverse effects on the condition of the turbine blade. Indeed, it would be advantageous to provide a system to estimate the condition of a wind turbine blade exposed to a lightning strike and/or to provide an estimate of the condition of the wind turbine blade resulting from the lightning strike.